I just noticed tonight that with the ignition on but the engine not running, there is a slight high pitched noise comming from the alternator. I know it's from the alternator as I disconnected it and it went away.

I'm wondering if this is normal or if the alternator is on the way out? I've had a problem with the battery going flat in a few days and thought it was the battery but a friend lent me a spare battery to try and it was when I was changing it that I noticed the noise.

Thanks for the help.

Robert

 

it shouldn't make any noise key on engine off.
sounds like its going out to me.

 

Well it turns out that the alternator is the cause of my batter going flat.

Thanks

 

Unlucky, but lucky. That is a problem that can really take forever to find. Lucky you heard the noise, unlucky you're stuck buying a new one.

 

Any idea on what was wrong with the alternator that was causing it do that? Before I put my car into storage last year I installed a new alternator and it was also making a faint high pitched oscillating whine with the engine off. And, I was also having trouble with a dead battery after a few days of not driving it. Hmm...what are the odds? This will be the first thing I check when I pull it out of storage this year. Hopefully this will be the culprit of my dead battery problems.

 

more than likely one of the diodes in the bridge rectifier are bad, if you know how to do it they can be checked with a DVMM by tearing the alt apart. you can buy & replace the parts if you want to. the last time i bought the parts to rebuild an alt was about 10 years ago, with the regulator, bridge rectifier, brushes, bearings & one other small part i can't think of the name of right now, it seems like i spent around $30.00 on it. took me about an hour to do. it saved me some bucks & was still working fine till the motor turned loose a couple of years later. of course doing this you have no warranty on it & if the windings or rotor are bad, your out the price of the parts.

 

In a way I'm glad it's the alternator, as someone said trying to find a drain could be a real headache...one that I can do without right now.

I'll probably get another one and then mess about with this one and see if it can be fixed. I'm in the UK so not sure how easy or expensive the repair would be.